Air-cooled, port-scavenged, two-stroke cycle engine with rotating piston



Sept. 8, 1959 P. H. SCHWEITZER ETAL 2,902,987

AIR-COOLED, PORT-SCAVENGED, TWO-STROKE CYCLE Filed Oct, 24, 1957 ENGINE WITH ROTATING PISTON :s Sheets-She et 1 INVENTORS 4/, elf/644061 W gel/1.48am

' ATTORN Y Sept. 8, 1959 P. H. SCHWEITZER ETAL 2,902,987 AIR-COOLED, PORT-SCAVENGED, TWO-STROKE CYCLE I ENGINE WITH ROTATING PISTON 3 Sheets-Shet 2 Filed Oqt. 24, 1957 INVENTORS 21% aetwo wmw,

ATT RNEY P. H. SCHWEITZER ETAL AIR-COOLED,

2,902,987 PORT-SCAVENGED, TWO-STROKE CYCLE ENGINE WITH ROTATING PISTON Sept. 8, 1959 3 Sheets-Sheet 5 Filed Oct. 24, 1957 INVENTORS Gig/104% 9X), JEMWMW,

United States Patent O AIR-COOLED, PORT-SCAVENGED, TWO-STROKE CYCLE ENGINE WITH ROTATING PISTON Paul H. Schweitzer and Albrecht W. Hussmann,

State College, Pa.

Our invention relates broadly to engines and more particularly to a construction of an air-cooled, portscavenged, two-stroke cycle internal combustion engine with rotatable pistons.

One of the objects of our invention is to provide an air-cooled, two-stroke cycle, port-scavenged internal combustion engine with a piston so mounted with respect to the piston rod that the piston rotates during the upstroke and downstroke of the piston for progressively presenting different contact surfaces circumferentially to the 'Wall of the cylinder for insuring uniform and symmetrical heating and wearing qualities in the cylinder and piston, thus preventing distortion and overheating.

Another object of our invention is to provide a construction of an air-cooled, two-stroke cycle, port-scavenged internal combustion engine in which the piston is mounted to rotate with respect to the piston rod, the piston containing inertia means effective under the force of upstroke and downstroke movements of the piston to cause rotation of same for presenting progressive circumferential surfaces thereof to the interior wall of the cylinder.

A further object of our invention is to provide a construction of an air-cooled, two-stroke cycle, port-scavenged internal combustion engine utilizing rotatable pistons which contain internally disposed cylindrical recesses disposed at an angle to the central axis of the piston and into which inertia capsules partially filled with mercury, sodium, salt, or the like are inserted for introducing a turning torquein the piston for revolving the piston in the course of the upstroke and downstroke movements thereof for presenting fresh surfaces of the piston to the internal walls of the cylinder thereby insuring uniform and symmetrical wearing properties in the piston and cylinder combination.

Still another object of our invention is to provide a construction of metallic capsule containing an inertia substance adapted to introduce a turning torque in a rotatable piston when inserted in the piston and the piston operated by upstroke and downstroke movements thereof for presenting fresh circumferential surfaces of the sidewall of the piston to adjacent interior surfaces of the cylinder of the air-cooled, two-stroke cycle, portscavenged internal combustion engine, in which the piston operates insuring uniform and symmetrical wearing and preventing overheating of the piston or the cylinder.

Other and further objects of our invention are to provide a construction of an inertia motor associated with an air-cooled, two-stroke cycle, port-scavenged internal combustion engine rotatable mounted piston on a reciprocating piston rod for subjecting the piston to a lateral rotating movement simultaneously with the upstroke and downstroke movements thereof for insuring uniform wear ing of and uniform heat distribution over the piston and the cylinder as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

Fig. l is a vertical sectional view through the air-cooled,

two-stroke cycle, port-scavenged internal combustion t ice 2 engine of our invention with rotatable piston showing the mounting of the rotatable piston on the piston rod thereof, in the extreme upstroke position, and the arrangement of motor means within the piston for insuring the lateral rotation thereof in the course of the upstroke and downstroke movements of the piston rod;

Fig. 2 is substantially the same view as in Fig. l but showing the piston rotated ninety degrees and in the extreme downstroke position with cylinder scavenging ports completely uncovered by the piston;

Fig. 3 is an enlarged view of the piston taken substantially on line 3-3 of Fig. 1 and illustrating the inertia motor means within the piston;

Fig. 4 is a transverse sectional view taken substantially on line 44 of Fig. l and showing the distribution of the inertia motor means within the rotatable cylinder;

Fig. 5 is an enlarged perspective view of the interior portion of the rotatable piston showing the arrangement of the inertia piston rotator within the piston;

Fig. 6 is an enlarged view showing the manner in which the inertia capsule is mounted within the piston.

Our invention is directed to an arrangement of an aircooled, two-stroke cycle, port-scavenged internal combustion engine with a rotatable piston which is revolved within the engine cylinder progressively in a fixed direction as the piston reciprocates within the cylinder. Our invention is particularly adaptable to air-cooled, twostroke cycle, port-scavenged internal combustion engines where long term operation is desired with minimum wear of the piston and the cylinder. The objective of our invention is to prevent distortion and possible overheating of the piston and of the cylinder in this type engine by causing the piston to rotate progressively within the cylinder and in so doing carry heat from the hot exhaust port region to the relatively cool intake port region. Without the provision of a rotating piston an air-cooled engine of the port-scavenged type is in grave danger of failure, because of the unsymmetrical heating of the piston and associated cylinders. This unsymmetrical heating is brought about in port-scavenged engines because the exhaust ports are disposed along one portion of the cylinder wall with the intake ports disposed adjacent to them. With this arrangement when the piston crown uncovers the ports to recharge and exhaust the cylinder, the hot gases always exit at one portion of the cylinder wall through the exhaust ports. Therefore, this region of the cylinder wall and that portion of the piston adjacent the wall are constantly being swept by hot gas when the ports are uncovered while the opposite cylinder wall and that portion of the piston adjacent to it are swept by cool air from the intake ports. If the engine is air-cooled and therefore there is no Water jacket to aid in distributing the heat evenly, the piston and cylinder, due to the uneven heat distribution, would warp and this distortion would cause the engine to overheat and eventually bind.

By providing means within a rotatably mounted piston on a reciprocating piston rod, the piston is progressively revolved simultaneously with the upstroke and downstroke movements of the piston rod for presenting a fresh circumferential surface of the piston to the internal circumferential wall of the cylinder thereby insuring substantially uniform and symmetrical wearing properties and heat distribution in the piston and cylinder combination. By. causing the piston to rotate, part of the heat from the hot exhaust port region is transferred to the relatively cool intake port region since on each upstroke and downstroke of the piston small increments of area on the hot portion of the piston are rotated opposite to relatively cool increments of area on the cylinder bore and small increments of area on the relatively cool portions of the piston are rotated opposite to relatively hot increments of area on,

the cylinder bore. In an inertia motor, consisting of cap= sules which are insertable into holes drilled into the interior of the piston at acute angles with respect to the central axis of the piston, reaction forces .due to the sloshing of the material within the capsules produce a turning torque which turns the piston during the upstroke and downstroke movements thereof.

Our invention will be more clearly understood by reference to the drawings in more detail wherein reference character 1 designates a port-scavenged, air-cooled, twostroke cycle internal combustion engine containing an aircooled cylinder 2 and crankcase 3. The cylinder wall is encircled with scavenging ports consisting of exhaust ports 37 and air intake ports 33. The exterior of the cylinder is encircled with cooling fins 39. The engine includes a central shaft 4 containing a crank represented at 5 which is driven by the connecting rod 6 secured to the crank 5 by suitable clamping bolts indicated at 7. The connecting rod 6 carries a piston thereon of the type described more fully in copcnding application Serial No. 471,287, filed November 26, 1954, by Paul H. Schweitzer, for Piston and Connecting Rod Assembly for Internal Combustion Engines, now Patent No. 2,815,993. The crown and cylindrical side of piston control the opening and closing of scavenging ports 37 and 38. In Figs. 1 and 2 we have illustrated an arrangement of slotted wrist pin 8 into which the end of connecting rod 6 extends. The wrist pin 8 is rotatably mounted in bearing sleeve 27 arcuately slotted at 28 for the entry of connecting rod 6. The wrist pin carrier 9 fits within the piston 10 in such manner that piston 10 is free to revolve about the wrist pin carrier 9. This rotation of piston 10 is illustrated in Figs. 1 and 2 by referring to the drilled holes 19 and 20, which will be discussed later. Fig. 2 shows piston 19 rotated ninety degrees clockwise from the position illustrated in Fig. l. A fastening bolt 32 extends through the end of connecting rod 6 and through the slotted wrist pin 8 for securing the connecting rod 6 to the wrist pin 8.

The rotary mounting of piston 19 with respect to the wrist pin carrier 9 is accomplished by arranging circular bearing surfaces 11 and 12 on the diametrically opposite exterior walls of the wrist pin carrier 9. The interior wall of the hollow piston 10 carries transversely aligned annular surfaces 14- and 15 interiorly of the hollow piston and bearing upon the circular bearing surfaces 11 and 12, respectively, of the wrist pin carrier 9. There is a circular recess 16 in the top of wrist pin carrier 9 into which the circular Wear plate 29 is inserted and toward which the central portion 17 of piston 10 extends, terminating in a fiat end 18 which abuts against the surface of wear plate 29 of central recess 16.

The head of the piston 10 at the central portion 17 thereof is drilled through the flat end face 18 as shown at 19 and 20. These drilled holes 19 and 20 are inclined in opposite directions at an angle with respect to the central axis of the piston. We have designated this angle as 0:, which is an acute angle with respect to the central axis through the piston. The drilled holes 19 and 20 extending in opposite angular directions receive the capsules shown at 21 and 22. These capsules consist of metal containers or pipes which may be swedged on opposite ends thereof as represented for example in Fig. 6, at 23 and 24. The capsules are first closed at one end and then filled through approximately one-half the volume thereof with a liquid forming a weighted heavy mass such as mercury, sodium, salt, or other substance which is liquid under engine operating temperature. After the capsules are filled through approximately one-half the volume thereof the open end is closed and the capsule inserted into the cavity formed by the drilled holes 19 and 20 in the head of the piston. The ends of the drilled holes in the surface 18 of the central portion 17 of piston 10 are then peened over the closed end of each capsule 4 as represented at 30 and 31 in Fig. 6 for maintaining the capsule 22 in position within the piston.

The assembly of the piston 10 on the connecting rod 6 is now completed by passing the wrist pin carrier 9 through the hollow end of the piston 10 so that the flat surface 18 of the end of the central portion 17 of the piston rests against wear plate 29 in the recessed head 16 in the wrist pin carrier 9. A snap ring 25 is snapped into position in a transverse groove 26 on the interior wall of hollow piston 10 beneath the annular surface 15 and beneath the depending walls 35 and 36 of the wrist pin carrier 9, thereby locking the connecting rod assembly to the piston while leaving the piston free to revolve in a transverse direction with respect to the axis of the con necting rod 6.

The reciprocation of piston 10 in the upstroke and downstroke cycles thereof, as illustrated in Figs. 1 and 2, respectively, causes the material or liquid in capsules 21 and 22 to slosh up and down. Inasmuch as the holes or cavities 19 and 20 are formed on axes which extend at acuteangles to the axis of the piston, the reaction force of the sloshing liquid develops a force vector component perpendicular to the transverse radii of the flat end 18 of the piston which causes the piston to rotate during the upstroke and downstroke movements of the connecting rod. If the two rotations were exactly equal but one in clockwise the other in anticlockwise direction the net piston rotation per revolution would be zero. However, if the frictional resistance to the rotation is greater during the deceleration and acceleration near the top center than during the deceleration and acceleration during the bottom center position of the piston, the rotation near bottom center will be greater than near top center and the piston will rotate in a jerkwise motion during the operation of the engine.

The piston tends to rotate because the liquid in motion in each capsule disposed at an acute angle to the piston motion or cylinder center axis exerts a pressure on the capsule wall at the point of contact between the slashing liquid and the capsule. This pressure at the point of contact creates a force vector or torque having one component parallel to the cylinder center axis and another component which is perpendicular to the radius which connects the center of the piston to the point of contact between the capsule and the sloshing liquid. This latter component tends to rotate the piston and will rotate it if there is no frictional resistance to the rotation or if this resistance is smaller than the reaction force causing the rotation. Therefore, the capsules are designed to create a rotating force greater than the frictional resistance forces.

The frictional resistance to rotation is greater when the force pressing the piston to the thrust surface (stool) is greater. The resistance force on the piston is the sum total of the gas force and the inertia force, The inertia force is negative (pointing upward toward the cylinder head) near top center and positive (pointing downward) near bottom center. The gas force, however, due to compressed gas pressure is much greater than the inertia force; therefore, the resistance to rotation will be greater at top center during the compression cycle than at bottom center during the intake and exhaust cycle. Thus the resistance and rotation forces acting on a properly designed piston in a two-stroke cycle engine balance out so that piston rotation near bottom center is greater than near top center since less frictional resistance is exerted upon the piston in the near bottom center position. Piston rotation in both the top center and bottom center positions is also consistently regular and symmetrical.

Referring to Fig. 2, this jerkwise rotating motion will rotate the piston in a clockwise direction as indicated at 40, thus moving the hot portion of piston 10 designated at 41, which is opposite the exhaust port 37 and which is swept by the hot exhaust gases, toward cooler cylinder bore areas in the vicinity of intake ports 38. The cooler cylinder wall then conducts some of the heat from the hotter piston to the cylinder cooling fins 39. Conversely, cooler portions of piston 10, designated at 42, since this portion of the piston is farthest from the hot exhaust exit area and is swept by cooling air from the intake ports 38, are rotated toward hotter portions of the cylinder bore in the vicinity of exhaust ports 37 and conduct some of the heat from the cylinder bore to distribute the heat more evenly over the cylinder-piston combination.

In order to prevent displacement of the capsules 21 and 22 from the inserted positions thereof in the piston head, these capsules are made to fit snugly in the drilled holes 19 and 20 and the material of the piston at face 18 thereof so displaced by peening that the capsules will not be shaken loose during the piston reciprocation. The sloshing of the liquid or material in the capsules 21 and 22 causes by the intertia thereof the progressive or creeping rotation of the piston during the upstroke and downstroke movements of the connecting rod.

While we have disclosed inertia means constituted by partially filled capsules located in position in the head of the piston to induce rotative movement of the piston, we realize that other forms of motor means may be provided for revolving the piston to insure the presentation of a fresh circumferential surface of the skirt of the piston to the inside cylindrical wall of the cylinder and we desire that it "be understood that our disclosure herein is to be considered in the illustrative sense and not in the limiting sense and that We intend no limitations upon our invention other than may be imposed by the scope of the appended claims.

What we claim as new and desire to secure by Letters Patent of the United States, is as follows:

1. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine comprising in combination an externally finned cylinder the bore of which contains exhaust and intake ports, a piston disposed within said cylinder, the crown of which opens and closes said exhaust and intake ports, a reciprocating connecting rod assembly, said piston mounted for rotatable movement on said connecting rod assembly and means contained within said piston beneath the top surface thereof for imparting rotary movement thereto during the upstroke and downstroke movements of said connecting rod assembly.

2. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine as set forth in claim 1, in which the means within said piston for imparting rotary movement thereto consists of an inertia motor for developing a rotative force component in said piston from the upstroke and downstroke movements of said connecting rod assembly.

3. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine as set forth in claim 1, in which the means within said piston for imparting rotary move ment thereto during the upstroke and downstroke movements of said connecting rod assembly consist of displaceable masses of material within said piston, the said masses of material being subject to mass movement as the connecting rod assembly reciprocates for imparting to said piston a momentum around the central axis of the piston for revolving the piston for presenting a fresh circumferential surface on the exterior of the piston to the interior wall of a cylinder with respect to which said piston coacts.

4. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine as set forth in claim 1, in which the means within said piston for imparting rotary movement thereto during the upstroke and downstroke movements of said connecting rod assembly consist of tubular capsules partially filled with a displaceable mass and mounted within said pistons in positions displaced from the central axis thereof and extending at acute angles with respect to said central axis for developing rotative force components transversely of the axis of said piston for revolving the piston about the axis thereof.

5. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine as set forth in claim 1, in which the means within said piston for imparting rotary movement thereto during the upstroke and downstroke movements of said connecting rod assembly consist of metallic capsules partially filled with mercury and mounted olfcenter in said piston for developing by the sloshing thereof within said piston a turning torque for revolving the piston about the central axis thereof.

6. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine as set forth in claim 1, in which the means within said piston for imparting rotary movement thereto during the upstroke and downstroke movements of said connecting rod assembly consists of metallic capsules partially filled with a displaceable mass, said metallic capsules being inserted in cavities extending interiorly of said piston and oif-center with respect to the central axis thereof and wherein the material of said piston on each side of said cavities on the interior of said piston is peened over said metallic capsules for maintaining said metallic capsules in position while the shifting of the displaceable mass induces rotation of the piston around its axis.

7. An air-cooled, two stroke cycle, port-scavenged internal combustion engine as set forth in claim 1, in which said means within said piston for imparting rotary movement thereto during the upstroke and downstroke movements of said connecting rod assembly consists of cavities formed interiorly of the piston and oif-center with respect to the axis thereof on longitudinal axes extending at acute angles to the central axis of said piston and partially filled capsules containing displaceable masses secured within said cavities for developing by the sloshing of the masses therein a turning torque for revolving the piston with respect to the connecting rod assembly.

8. An air-cooled, two-stroke cycle port-scavenged internal combustion engine as set forth in claim 1 in which said means within said piston for imparting rotary movment thereto during the upstroke and downstroke movements of said connecting rod assembly consist of a mass of mercury displaceable within said piston for developing a force component around the axis of said piston.

9. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine as set forth in claim 1 in which the means within said piston for imparting rotary movement thereto during the upstroke and downstroke movements of said connecting rod assembly consist of a displaceable mass of sodium moveable eccentrically of the axis of the piston.

10. An air-cooled, two-stroke cycle, port-scavenged internal combustion engine as set forth in claim 1 in which the means within said piston for imparting rotary movement thereto during the upstroke and downstroke movements of said connecting rod assembly consist of a displaceable mass of salt moveable eccentrically of the axis of the piston.

References Cited in the file of this patent UNITED STATES PATENTS 

